Dear @hanhechong ,
Apologies for the late reply to your questions:
Question 1: I believe this also refers to another question of yours, for which it seems required that you call USRDCI explicitly within mdstck.f. In the last entry of this post you can find an mdstck.f example to debug your routine and get the correct ancestors (by disregarding the neutrons for example).
Question 2: I am not sure your transcript of the dump file is complete. If you simulate in semi-analogue mode the entire decay chain is created explicitly since FLUKA doesn’t keep the timing information on creation of residual nuclei so when the next particle in the chain appears the previous one will not be there anymore: for this reason all of them end up in the decay chain. If you provide us the muon.txt file you use as source we could replicate your results and also look at the other variables dumped.
Question 3: Have you looked at the ICODE variable for this reaction? I believe these you also print out each time in the routine so this should clarify this?
Best regards,
Andreas